Gestational diabetes mellitus frequently causes skin dryness due to impaired microcirculation, peripheral neuropathy, and reduced sweat gland function, increasing the risk of skin infection and decreasing maternal quality of life. Natural topical products containing bioactive compounds may provide a safe alternative for improving skin hydration during pregnancy. This study aimed to determine the most effective concentration of Loranthus sp. liquid soap for improving skin moisture in pregnant women with gestational diabetes mellitus. A quasi-experimental study using a nonequivalent control group design was conducted at the Tilango Community Health Center, Gorontalo Regency, Indonesia. Thirty pregnant women with gestational diabetes mellitus were allocated into three intervention groups receiving Loranthus sp. liquid soap containing 5%, 10%, or 15% extract (n=10 per group). Participants used 500 mL of the assigned soap twice daily for seven consecutive days. Skin moisture was measured before and after the intervention using digital skin moisture analyzer EH900U. Within-group differences were analyzed using the Wilcoxon signed-rank test, while differences among intervention groups were assessed at a significance level of 0.05. Mean skin moisture increased from 34.6±3.1% to 37.1±5.1% in the 5% group, from 34.8±4.8% to 37.9±4.9% in the 10% group, and from 37.0±5.3% to 45.6±4.3% in the 15% group. Significant improvements were observed in all groups (p=0.041, p=0.026, and p=0.0001, respectively), with a significant difference among concentrations (p=0.0017). The 15% Loranthus sp. liquid soap demonstrated the greatest improvement in skin moisture and showed potential to improve skin moisture in pregnant women with gestational diabetes mellitus. Further studies with larger sample sizes, longer follow-up periods, and an appropriate control group are needed to confirm these findings.